The present invention generally relates to a piston pin, and in particular to a piston pin for connecting a piston to a connecting rod especially but not exclusively for an internal combustion engine. The present invention also relates to a method of making such a piston pin.
Piston pins, also called wrist pins, are known in many designs for connection of a piston to the connecting rod in piston-operated engines or equipment, like combustion engines. They can be formed out of solid material or embedded in a slotted sleeve, as disclosed in German Pat. No. 956 551. These piston pins typically are made from a permanently elastic core and a wear-resistant outer sleeve. Their drawback is a relatively large weight since piston speeds in Otto and Diesel engines average 20 m/sec. Thus, the inertia acceleration forces on piston pins are quite high. Piston pins can also be tubularly shaped, as disclosed in German patent specification no. 35 25 577, or may be made of several layers, as disclosed in German Patent Nos. 30 09 424 and 30 23 204. Also these types of piston pins are characterized by a comparably high weight and high inertia acceleration forces associated therewith.
A further drawback of all these types of piston pins is their relatively high manufacturing costs, as removal of material is involved when a piston pin is cut from a solid material or from rod material. Material removal processes require suitable machinery as well as the utilization of appropriate lubricants and coolants. In addition, the environmentally adequate disposal of scrap, lubricant and coolant usually also results in high energy cost.